(1) Field of the Invention
This invention relates to a technique for applying protective tape to a wafer surface with a pattern formed thereon and for separating the protective tape.
(2) Description of the Related Art
In a conventional process of manufacturing semiconductor wafers, a mechanical method such as grinding or polishing, or a chemical method including etching, is used to process the back surfaces of semiconductor wafers (hereinafter simply called xe2x80x9cwafersxe2x80x9d) to reduce the thickness thereof. When these methods are used to process the wafers, a protective tape is applied to the front surfaces of wafers in order to protect the front surfaces having wiring patterns formed thereon.
When a wafer is sent to a back-grinding process, the front surface (patterned surface) is suction-supported by a chuck table and the back surface is ground with a grinder. At this time, a protective tape is applied to the front surface to avoid the pattern being damaged under the stress of grinding occurring to the front surface, and to avoid contamination of the pattern.
The wafer thinned by grinding of its back surface could easily be broken during the processing or transportation. The wafer, due to its deflection or bending, is difficult to handle. In order to avoid such inconveniences, a proposal has been made to apply two different types of protective tape to a wafer surface beforehand to prevent damage and bending of the wafer (see Japanese Patent Publication (Unexamined) 2000-331968).
Thus, a method has been proposed and implemented to separate in a separating step, all at a time, the two types of protective tape applied to the surface of the wafer.
The use of protective tape in double plies as described in the above Japanese Patent Publication (Unexamined) 2000-331968 has an advantage in terms of wafer reinforcement, but has the following inconveniences encountered in the process of separating the protective tape.
When separating the protective tape in two plies all at once, it is sometimes impossible to separate the tapes at a time because of adhesive strengths of the first protective tape applied to the surface of the wafer and the second protective tape applied thereto. That is, the first protective could remain on the surface of the wafer.
In such a case, it is difficult to determine whether the first protective tape remains on the surface of the wafer or not.
The following problems arise when the number of protective tapes separated from the wafer cannot be recognized reliably.
When it is determined that only one protective tape is separated though the two protective tapes have been separated together, a separator tape is applied to the surface of the wafer to contaminate or damage the surface of the wafer.
Further, when a protective tape remains on the surface of the wafer, the separating step must be repeated twice, hence an inconvenience of lowering operating efficiency.
This invention has been made having regard to the state of the art noted above, and its primary object is to provide a protective tape applying and separating method capable of easily applying and separating protective tape to/from semiconductor wafers while reinforcing the wafers by giving rigidity thereto.
The above object is fulfilled, according to this invention, by a protective tape applying and separating method for applying protective tapes to a surface of a semiconductor wafer with a pattern formed thereon, and separating the protective tapes from the surface of the semiconductor wafer, the method comprising an applying step for applying a plurality of protective tapes in plies to the surface of the semiconductor wafer such that a protective tape with strong adhesion lies on top, and a separating step for applying a separator tape over the protective tapes applied in plies, and separating all at a time the protective tapes in plies from the surface of the semiconductor wafer by means of the separator tape.
With the protective tape applying and separating method according to this invention, the protective tapes are applied in plies, with a protective tape with strong adhesion lying on top, to the surface of the semiconductor wafer. Since the upper protective tape is stronger in adhesion than the lower protective tape, the lowermost protective tape, i.e. the protective tape applied directly to the surface of the semiconductor wafer, first separates from the surface of the semiconductor wafer. As a result, the protective tapes in plies are separated together from the surface of the semiconductor wafer.
Preferably, the protective tapes applied to the surface of the semiconductor wafer comprise two protective tapes bonded together in plies as a unit beforehand.
The protective tapes are applied as bonded together beforehand as a unit to the surface of the semiconductor wafer. The protective tapes applied in plies to the surface of the semiconductor wafer are separated together from the surface of the semiconductor wafer in one separating operation.
Preferably, at least an upper one of the protective tapes applied in plies is an ultraviolet curable protective tape. It is further preferable that ultraviolet light is emitted to the protective tapes applied in plies to the surface of the semiconductor wafer.
At least the upper protective tape of the protective tapes applied in plies to the surface of the semiconductor wafer is an ultraviolet curable protective tape. The adhesive of the ultraviolet curable protective tape is cured by performing an ultraviolet irradiating treatment of the protective tapes applied in plies, to adhere firmly to the surface of the lower protective tape. Thus, the protective tapes in plies are separated together from the surface of the semiconductor wafer in one separating operation.
Preferably, the lower one of the protective tapes applied in plies is an ultraviolet curable protective tape, and ultraviolet light is emitted before the protective tapes are separated from the semiconductor wafer.
Of the protective tapes applied in plies to the surface of the semiconductor wafer, an ultraviolet curable protective tape is applied directly to the surface of the semiconductor wafer. After the protective tapes are applied in plies to the surface of the semiconductor wafer, ultraviolet light is emitted before separating these protective tapes in plies, and then the protective tapes are separated. Consequently, the protective tape applied directly to the surface of the semiconductor wafer is cured to lower its adhesion, thereby facilitating separation from the semiconductor wafer.
In this invention, for example, the upper one of the protective tapes applied in plies may be a non-ultraviolet curable protective tape, or the lower one a non-ultraviolet curable protective tape.
Further, the lower protective tape of the protective tapes applied in plies has a rough surface.
Since the lower protective tape has a rough surface, the adhesive of the protective tape applied thereon enters the bulges and dimples of the surface of the lower protective tape. Thus, an area of adhesion is enlarged, and the upper protective tape adheres firmly to the lower protective tape.
Preferably, the protective tapes in plies are repeatedly applied as two separate protective tapes. Where two protective tapes are applied separately and repeatedly, for example, it is preferred that at least an upper one of the protective tapes applied in plies is an ultraviolet curable protective tape. It is further preferable that ultraviolet light is emitted to the protective tapes applied in plies to the surface of the semiconductor wafer, or the protective tapes may be bonded together and ultraviolet light emitted in a feeding step preceding application of the protective tapes to the surface of the semiconductor wafer.
The protective tapes are applied separately such that the first protective tape is applied to the surface of the semiconductor wafer, and then the second protective tape is applied to the surface of the first protective tape, and then ultraviolet light is emitted toward the protective tapes. Alternatively, ultraviolet light is emitted toward the protective tapes after the protective tapes in plies are bonded together in a feeding step preceding application of the protective tapes to the surface of the semiconductor wafer. When ultraviolet light is emitted, the adhesive of the ultraviolet curable protective tape is cured to bond the protective tapes firmly together. Thus, the protective tapes in plies are separated together from the surface of the semiconductor wafer in one separating operation.
Preferably, a lower one of the protective tapes applied in plies is an ultraviolet curable protective tape, and ultraviolet light is emitted before the protective tapes are separated from the semiconductor wafer.
Of the protective tapes applied in plies to the surface of the semiconductor wafer, an ultraviolet curable protective tape is applied directly to the surface of the semiconductor wafer. After the protective tapes are applied in plies to the surface of the semiconductor wafer, ultraviolet light is emitted before separating these protective tapes in plies, and then the protective tapes are separated. Consequently, the protective tape applied directly to the surface of the semiconductor wafer is cured to lower its adhesion, thereby facilitating separation from the semiconductor wafer.
In this invention, for example, the upper one of the protective tapes applied in plies may be a non-ultraviolet curable protective tape, or the lower one a non-ultraviolet curable protective tape.
Preferably, the lower protective tape of the protective tapes applied in plies has a rough surface.
Since the lower protective tape has a rough surface, the adhesive of the protective tape applied thereon enters the bulges and dimples of the surface of the lower protective tape. Thus, an area of adhesion is enlarged, and the upper protective tape adheres firmly to the lower protective tape.
This specification discloses the following solution also.
(1) A separating method for separating different types of ultraviolet curable protective tapes applied to a surface of a semiconductor wafer with a pattern formed thereon, the method comprising:
an ultraviolet irradiating step for emitting ultraviolet light with a wavelength varied according to the types of ultraviolet curable protective tapes; and
a separating step for separating the protective tapes treated with the ultraviolet irradiation.
For example, to give rigidity to the semiconductor wafer-formed thin, different types of protective tape are applied in plies to the surface of the semiconductor wafer. The protective tapes applied in plies are to be separated from the semiconductor wafer in one separating operation. However, because of the difference in adhesion between the protective tapes, all the protective tapes may not be separated from the surface of the semiconductor wafer in one separating operation.
According to the invention (1) above, different types of ultraviolet curable protective tapes are applied in plies to the surface of the semiconductor wafer, and ultraviolet light with a wavelength varied according to the types of ultraviolet curable protective tapes is emitted individually. Each ultraviolet curable protective tape is exposed to the ultraviolet light having a different wavelength. Thus, while the mating surfaces of the protective tapes are firmly bonded by curing of the adhesive, the protective tape applied to the surface of the wafer is cured to be easily separable from the surface of the wafer. As a result, the protective tapes in plies may be separated together from the surface of the semiconductor wafer at a time in one separating operation.